1. Field of the Invention
The present invention relates to a method of adhering soldering material, and more particularly to a method of applying a soldering material to a connecting member to which a connecting line is to be coupled by thermal welding.
2. Description of the Related Art
Commutators for electric motors are known, such as, for example, connecting members, to which connecting lines are respectively coupled by thermal welding.
The commutator has "claw"-shaped connecting portions (segments thereof) to which windings for an armature coil are electrically connected by, for example, resistance welding. The commutator, however, has a problem in that the electrical resistance between the claw-shaped connecting portions and the coil windings is increased due to the expansion and contraction of respective parts produced at the time of occurrence of a substantial difference in temperature between the parts to which the windings are connected (attached by applying pressure only) to the claw-shaped connecting portions. Since a slight interval is defined between each of the claw-shaped connecting portions and the respective windings, the commutator is prone to oxidation. In this case, too, there is a similar problem to that mentioned above in that the electrical resistance is increased.
Therefore, a method is known wherein soldering material is applied in advance to claw-shaped connecting portions of the commutator referred to above and thereafter re-melted by heat produced at the time the windings are electrically connected (attached by pressure) to the claw-shaped connecting portions, so as to cause the periphery of each of portions where the windings are electrically connected to the claw-shaped connecting portions to be covered with the molten soldering material, thereby preventing any increase in electrical resistance due to either thermal expansion and contraction or to oxidation.
As methods of adhering soldering materials to connecting members such as commutators, etc. to which connecting lines are to be electrically connected by thermal welding, there are known various methods such as a barrel-type electrolytic plating method, a melt plating method or a method of forming a laminated plate to which a soldering material is applied in advance in the form of a cylinder. The method of adhering a soldering material to the claw-shaped connecting portions of a commutator by barrel-type electrolytic plating, for example, is normally used, because large production capacity can be ensured.
For the above-described barrel-type electrolytic plating method, however, large equipment needs to be provided, (for example, an electrolytic plating apparatus), and it is absolutely necessary to provide acidic waste-liquid processing facilities. It is also necessary to perform pre-processing such as cleaning using acid solution, to enable reliable application of the plating process to commutators or the like.
According to the melt plating method, the plating process can be carried out by small equipment or simple effluent treatment facilities. However, this method has the problem that the adhered soldering material is thick and the amount of soldering material to be used must be large due to the oxidation of the soldering material.
Thus, conventional soldering material adhering methods have problems in that the soldering material is adhered to portions other than those portions to which the member to be connected is electrically connected to the connecting lines, i.e., portions to which it is unnecessary to apply the soldering material. Therefore, the amount of the soldering material which adheres to the portions referred to above other than those at which the lines are to be connected is increased and the manufacturing cost of a commutator is high. For this reason, it has been proposed that masking be applied to the portions to which it is unnecessary to apply soldering material, so as to prevent the soldering material from adhering to such portions. However, this approach takes time, and the production efficiency of the commutator is greatly reduced and hence its manufacturing cost becomes high.